In recent years, the availability of oil and gas has failed to keep up with the demand for energy in the United States and other countries. This state of affairs has contributed to the rising cost of oil and gas and to what is commonly referred to as an "energy crisis." There is not only concern for the security and economic well being of citizens but also concern for the availability of energy for heating of homes and other buildings. As a result of these concerns, research and development effort has focused on the development of alternative energy sources. Although such alternative energy sources include nuclear and other sources, a particularly attractive energy source is solar energy. In fact, various federal and state tax credits are given in the United States to encourage development and use of solar energy technology.
However, solar heating systems encounter several problems which must be overcome in order for such systems to be cost effective. One problem which must be overcome in order for a solar space heating system to be practical is that during the winter when there is the greatest need for heating energy, there is relatively less sunlight available than during the summer. Also, during the summer a conventional solar heating system does not contribute to cooling of the home. In short, at their present state of development it is generally not economically practical to purchase and use a conventional solar heating system which typically relies on glazed solar panels. Glazed solar panels are expensive and generally not cost-effective for space heating and cooling. As a result, few heating systems rely only on the sun to heat the interiors of buildings.
Thus, combination systems have been proposed where solar panels are used in combination with an auxiliary heating source such as an air source heat pump. The heat pump supplements the solar panels when the heating demand exceeds the capacity of the solar system. An additional electric resistance heating system may also be required to supplement the heat pump when the heating demand exceeds its capacity. However, such systems have several disadvantages. Air source heat pumps collect heat from the air alone and do not store heat from air at higher day time temperatures for use at night. Night, obviously, is usually the time period of greatest heating demand. This time/-temperature relationship is important as the Coefficient of Performance (COP) of the heat pump and the heat output capacity thereof are dependent on the temperature of the heat source. Thus, at the time of greatest heating demand, the air source heat pump is the least efficient and has the least heat output capacity. Another problem with use of air source heat pumps is the formation of frost on the outdoor air heat exchange coil. If left unattended, frost will at times block heat transfer from the outside air to the heat pump. Heat pump COP and heat output capacity decline as frost accumulates. This problem is generally dealt with by an energy expensive defrosting of the outdoor coil. In an air source heat pump, defrosting is usually accomplished by running in the air conditioning mode, i.e. withdrawing heat from the interior of the building to melt the frost. The continual reversal of valves and refrigerant is hard on the unit. Service life and reliability of the air source heat pump are adversely affected by the defrost cycle.
It is manifest that it would be desirable if an economically practical solar heating system could be provided. This is an object of the present invention wherein an efficient, solar assisted, reversible heating system is provided. The system of the present invention employs relatively inexpensive, uncovered panels to collect heat from the sun and/or from the ambient air. The collected heat is transported by fluid to a storage tank which provides a source of heat for a water source heat pump. The system can be reversed for summer cooling.
The reversible heating system of the present invention efficiently uses energy and involves relatively inexpensive components which can be easily installed and serviced. Further features, advantages and understanding of the present invention will be obtained from the following disclosure taken in conjunction with the appended claims and accompanying drawings.